Narcotic dependence has been attributed to changes in the activity of central nervous system synapses. A number of neurochemical processes which underly this altered synaptic activity are regulated by mechanisms involving the phosphorylation of proteins. Phosphorylative activity may represent, therefore, one of the key sites of molecular adaptations accounting for the long lasting effects induced by drugs of abuse. We have reported (Ehrlich et al., Life Sci. 23:127-136, 1978) that short-term (3 days) exposure of rats to morphine induced general increase in the phosphorylation of neostriatal-membrane proteins. Long-term (3) weeks) exposure to incremental doses of morphine resulted in selective decrease (50 percent and 70 percent respectively) in the phosphorylation of specific proteins designated F and H (M.W. 47K and 10-20K). The present project intends to: (1) elucidate the mechanisms by which narcotic drugs induce these phosphorylative adaptations. (2) Determine the specificity of the observed effects to morphine, (3) investigate the role of phosphoproteins F and H in the function of opiate-receptors, and (4) isolate and purify these proteins. Regarding the mechanism, our research progress thus far has established that the phosphorylation of proteins F and H is inhibited in vitro by physiological concentrations (0.1-1nM) of the opioid peptide beta-endorphin. Higher concentration (1-10nM) of beta-endorphin or etorphine stimulate Ca ions-dependent phosphorylation in the membranes, and this effect is blocked by the antagonist naloxone (1 micronM). With respect to specificity, we have found that long term (8 weeks) alcohol exposure induces increase in Ca ions-dependent phosphorylation, but a decrease in F and H (characteristic of opiates) was not in evidence. In addition, ongoing studies provide data indicating that protein phosphorylation is involved in the regulation of adenylate cyclase activity, and that endogenous phosphorylation systems may constitute part of the opiate receptor complex. Taken together, the data suggest that protein phosphorylation may serve as a transducing mechanism in the function of opiate receptors, and that specific adaptations in this enzymatic machinery may play a role in processes underlying the development of narcotic dependence.